Small glaciers account for most of Greenland's recent loss of ice

Washington, September 16 : A new study has shown that rather than large glaciers, it is the small ones that account for most of Greenland's recent loss of ice.

The study shows that the dozens of much smaller outflow glaciers dotting Greenland's coast together account for three times more loss from the island's ice sheet than the amount coming from their huge relatives.

Reports indicate that nearly 75 percent of the loss of Greenland ice can be traced back to small coastal glaciers.

According to Ian Howat, an assistant professor of earth sciences and researcher with Ohio State's Byrd Polar Research Center, their discovery came through combining the best from two remote sensing techniques.

"It provides perhaps the best estimate so far of the loss to Greenland's ice cap," he said.

Aside from Antarctica, Greenland has more ice than anywhere else on earth. The ice cap covers four-fifths of the island's surface, is 1,491 miles (2,400 kilometers) long and 683 miles (1,100 kilometers) wide, and can reach 1.8 miles (3 kilometers) deep at its thickest point.

As global temperatures rise, coastal glaciers flow more quickly to the sea, with massive chunks breaking off at the margins and forming icebergs.

While some of the largest Greenland glaciers - such as the Jakobshavn and Petermann glaciers on the northern coast - are being closely monitored, most others are not.

Howat and his colleagues concentrated on the southeastern region of Greenland, an area covering about one-fifth of the island's 656,373 square miles (1.7 million square kilometers).

They found that while two of the largest glaciers in that area - Kangerdlugssuaq and Helheim - contribute more to the total ice loss than any other single glaciers, the 30 or so smaller glaciers there contributed 72 percent of the total ice lost.

"We were able to see for the first time that there is widespread thinning at the margin of the Greenland ice sheet throughout this region," he said.

"We're talking about the region that is within 62 miles (100 kilometers) from the ice edge. That whole area is thinning rapidly," he added.

Howat said that all of the glaciers are changing within just a few years and that the accelerated loss just spreads up deeper into the ice sheet.

To reach their conclusions, the researchers turned to two ground-observing satellites, which revealed two data sets.

"We simply merged those data sets to give us for the first time a picture of ice elevation change - the rate at which the ice is either going up or down - at a very high (656-foot or 200-meter) resolution. They are a perfect match for each other," Howat said.

"What we found is the entire strip of ice over the southeast margin, all of these glaciers, accelerated and they are just pulling the entire ice sheet with it," he added.